Answer:
All real numbers except 1
Any (x, y) coordinates that fall in the red are applicable.
(5, -5)
(10, -8)
etc
Note that the Area of a rectangle is given by
Area = LB
Where L is the Length (the longer side) and B is the Breadth (or Width which is the shorter side).
From the image, L is (x+6).
Also from the image, B is (x+2)
This implies:

Open up the bracket by multiplying both terms:

Since the question says to leave it in polynomial form, that is your answer. Hope I helped? ☺️